Furnace Troubleshooting: 7 Gas Furnace Solutions

There’s nothing worse than waking up on a winter day to a home that feels as cold inside as the temperature outside! If this is a situation you’ve found yourself in, a furnace not working could be what’s causing your chilly mornings.

While you need to call an HVAC professional right away if you smell gas or hear strange noises coming from your furnace, in some cases the problem can be minor and you might be able to do some furnace troubleshooting on your own. Here’s our list of seven gas furnace troubleshooting solutions that are safe for you to try.

WARNING: Attempting to repair your furnace yourself can have major safety and health consequences. If your furnace is powered by natural gas, improper repair can result in dangerous leaks that can expose your family to toxic fumes and the risk of explosions. Electric furnaces can shock you during wiring work. Always consult a licensed HVAC professional if you are experiencing mechanical issues with your furnace.

Check these seven furnace troubleshooting tips before you call in the pros.

The problem might not even be your furnace at all — it may be your thermostat! Before you call a professional, check your thermostat and make sure it’s on. It’s possible your thermostat may need new batteries or was just switched off by mistake. Once you ensure your thermostat is on, make sure it’s set to ‘heat’ at a temperature at least five degrees above room temperature.

Your furnace functions by making heat, then pumping that hot air through all your vents to, ultimately, raise the temperature. If your home isn’t feeling warm, but your furnace is on, make sure all your vents are completely open. Vents can be found on the floor, ceiling, or walls in each room of your home. If they’re blocked or closed, heat will not be able to flow.

If you feel like your furnace is still producing some heat, but not enough, the culprit could be a clogged or dirty furnace filter. All HVAC systems, including furnaces, heat pumps, cooling devices and more, have filters that homeowners should change regularly.

The first step in checking your furnace filter is locating it, but before you do that ensure your furnace is completely turned off. The filter is always situated near the blower, which is the part of your furnace where hot air exits so it’s blown throughout your home. Exactly where your blower is located depends on how your furnace was installed:

If you have a horizontal-facing furnace, the blower will be on the side and the filter will be slid into a rack.

If you have a vertical-facing furnace, the filter will be in either the top or bottom doors, depending on whether air is flowing upward or downward through the blower.

If your furnace is not heating, it might not be getting any power to produce any heat. First, check the general power switch on your furnace. Make sure no one in your home hit it and flipped it off by accident. If that switch is still on, find your home’s main electrical panel and look for the switch labeled ‘heat’ or ‘furnace.’ Make sure that’s also on, and toggle it back and forth between on and off one time. If this results in a fuse blowing, contact an HVAC professional because there may be a bigger furnace problem at hand.

In older furnace models, a blue, even flame should be visible through the opening in your furnace at all times. Newer models use an electric ignition system that only lights when necessary, so they don’t have these flames. If your furnace does have a flame, and you see yellow or uneven flames instead of blue ones, you may have dirty burners or burners blocked with debris. If you notice this furnace problem, call an HVAC professional and schedule furnace and burners maintenance.

As we mentioned earlier, older model furnaces burn visible blue flames. If your furnace has a blue flame, it’s lit by the pilot light. On the other hand, newer model furnaces function with an electric ignition that eliminates the need for a constant flame.

If your furnace has a pilot light, it will be controlled by a knob on the bottom of your unit. You can easily relight the pilot light by turning the knob to ‘off,’ waiting a minute, then setting it back to ‘on.’ This will stop and restart the gas flow of your furnace.

If you have a newer furnace with an electric igniter contact an HVAC professional for advice on next steps.

Your furnace’s gas valve is made up of two valves: the safety valve, which supplies gas to the pilot light, and the main valve, which supplies gas to the burner trays. If your pilot light isn’t on, make sure the gas valve, located in the service panel on the side of the furnace, is on and supplying gas to the pilot light. If you suspect you have a gas leak, LEAVE YOUR HOME IMMEDIATELY and call 9-1-1, then contact an HVAC professional immediately from a safe location.

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